A project seeking to help integrate more rooftop solar into Australia’s grid and increase export limits is about to kick off.
In some parts of Australia solar owners are unable to export surplus electricity they generate, or only a fraction of it, due to network constraints resulting from very high adoption of PV systems. Excessive levels of exported solar energy may only occur during certain times of the day, but these export limits apply all day.
While installing solar panels can still make sense for zero-export homes, the situation not only adversely affects some existing solar owners; it can also be a barrier to further uptake of PV.
An ARENA supported SA Power Networks led trial will see flexible connection technology enable solar power systems to automatically adjust export limits based on network conditions.
The 12- month Flexible Exports field trial will involve 600 rooftop solar customers in South Australia and Victoria. In Victoria, SA Power Networks will partner with AusNet Services; which will lead the trial in that state. Also involved are solar inverter manufacturers Fronius, SMA and SolarEdge, and energy management firm SwitchDin.
We’ve mentioned SwitchDin here on SQ a few times in the past. Last year the company was chosen by Horizon Power to provide special controllers to accommodate high levels of small-scale solar and batteries in Western Australia’s Onslow region. The Secure Gateway Devices’ (SGDs) are called “Droplets”, and among other functions provide feed-in management.
“To date, we’ve integrated with close to three dozen inverter and battery brands to provide a ‘universal translation’ and enable easy communications at scale for network operators,” said SwitchDin CEO Dr Andrew Mears.
SwitchDin also recently announced it has been listed as a compatible technology solution with SA Power Networks’ Relevant Agent service in relation to the recently introduced “remote disconnect” requirements, and that its solution is available with no subscription costs for end users (further info here).
The Flexible Exports trial will involve participants’ smart inverters automatically adjusting electricity exported every 5 minutes to match the available capacity of the grid. Exports will only be curtailed at times when the network is constrained, rather than a permanent limitation such as is currently the case in affected areas.
$2 Million From ARENA
The Australian Renewable Energy Agency is stumping up $2.09 million in funding to SA Power Networks for the $4.84 million trial Flexible Exports project.
“This trial builds on ARENA’s efforts to encourage and support innovation in enabling technologies and in new ways of managing distributed energy to allow Australian families and businesses to confidently adopt clean energy technologies,” said ARENA CEO Darren Miller.
SAPN Really Getting Its Solar Game On
SA Power Networks has a target of enabling double the amount of solar power capacity it can accommodate on its network by 2025.
“We are looking at smart solutions, rather than expensive network capacity investment, to help make it happen,” said SA Power Networks General Manager Strategy and Transformation, Mark Vincent.
Flexible grid connection is just one approach SAPN is taking – SQ’s Ronald discussed flexible exports and optimizing network voltages in more detail recently.
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Rather than just switching down the power to limit the peaks every 5 minutes, would it not be a whole lot smarter to enable the system to switch on the off peak tariff meter for 5 minutes and draw power into the electric hot water service? Thus all power opportunity is useful rather than wasted, with the same net equalisation benefit.
Tim C
Load switching and new flexible storage loads eg hot water, batteries, EVs, pool pumps will all help to reduce the number of hours that the capacity might be exceeded.
There will still be locations with export limitations (albeit for less hours per year, and perhaps for less locations). This trial will enable as much solar to be exported as possible at the trial locations whilst living within the physical constraints of the local network.
Benje
This still doesn’t make sense. If the existing Grid-Tie Inverters are designed to limit their feed in power based on the line voltage, what is the problem?
Or is it that existing Inverters don’t actually do this?
I’ve asked this questions multiple times now with no answer.
Hi Fred,
In addition to Benje’s answers below, here are two further problems with relying on over-voltage curtailment:
1. It kicks in when the voltage is well above the target 230V. Relying on volt-var or volt-watt responses will result in voltages being at the upper limits for much of the time, at a level that appliances are not optimised for.
2. It’s not equitable. Those at the end of the LV circuit experience higher voltages than those closer to the transformer. Relying on voltage limits unfairly curtails those at the end. The “flexible exports” system should allow a more equitable sharing of the losses
Fred
there are two different issues:
1. congestion on the local LV distribution grid. If exports exceed the capacity of the local network, then outages occur. If the voltage is lowered dynamically (which allows more PV to be exported before voltage limits are exceeded) then some control is required to prevent the local network being overloaded. Voltage doesn’t necessarily reflect the remaining network thermal capacity for more PV export.
2. State minimum demand. If SA generation exceeds SA load and export via interconnection capacity, then the system is unstable. Scheduled generation is wound back to minimum stability levels, and semi-scheduled generation (wind, solar farms) may also be wound back. Some smaller-scale generation may need to be wound back on exceptional days.
Hope this helps.
Thanks Benje,
But neither point address the main issue….
If there is excess Solar generation, then the Voltage will rise, which in turn automatically reduces the solar contribution (as the grid-tie inverters back off).
Obviously the risk is where solar supply exceeds (or approaches) the local load.
But to avoid that, the main generators need only allow the Voltage to rise above the level where the grid-tie Inverters will back off.
It seems that the real issue is that the resistance (eg impedance) of the supply lines is so high that the main generators can no longer control the voltage or Frequency even at the nominal Voltage.
Which means that unaided (eg the without the Solar contribution) the local supply would have suffered a brown-out or a total blackout.
Which simply says that expenditure on the power grid has not kept pace with the increased demand for power.
Sorry, but both of these arguments sound a bit specious.
Most appliances these days use switch-mode supplies, and these are perfectly happy with quite extreme voltage excursions..
And the consumers at the end of the line have been complaining about low voltages for generations.
All of the points raised so far underline the real problem: That our aging power grids are not coping as our demand for power increases.